During slow times at Nomad, I put together this helpful website,
to help our customers get there files ready for print.

Unfortunately, there were fewer and fewer slow days,
so I never got around to putting the finishing touches on it.

I'm still proud of it, so take a look!

or return to my portfolio index

Nomad Nomad Printing and Services presents
Hints for a sucessful print job This digital guide will show you how
to set up your files to go to press,
as well as hints and tips
for good print design


last updated : 2003.02.11

«Section One»        General Prepress Hints
«Section Two»        Photoshop - Raster Art
«Section Three»      Illustrator - Vector Art
«Section Four»       Quark - Layout and Design

Section One

A Brief history of Printing

Color Theory

Digital File Formats and Information

Introduction

This is your quick n' dirty guide to the arcane world of modern color printing.
This website will help you prepare your files to print the way you intend, without unpleasant and expensive surprises.

Each section is designed to explain an important concept in electronic printing.

This Section introduces general printing concepts and color models, plus some information on file formats.
Section Two explores Adobe® PhotoShop and bitmap art, plus some helpful hints.
Section Three explores Adobe® Illustrator and vector art, besier curves, and some hints how to use fonts in your print job.
Section Four covers how to use page layout applications for your print job, focusing on Quark® Xpress.


Quark, Illustrator, and PhotoShop are the workhorses of modern printing.
Even if you don't use these particular applications,
the concepts introduced are applicable to any print job.

A brief history of printing


Printing is an old technology. The roots of modern printing lay in the 15th century, with the first presses used in Europe. These presses were based on wine presses, and they used a big piece of carved wood to press ink onto paper. This slab of wood was called a printing plate, and craftsmen carved these plates by hand. The presses were big, slow, and hard to get consistent results with. And once a wood plate broke, or warped, or cracked, the printer had to start all over from scratch. In the early days, printing was more of a craft than a science.

In the 1800s, printing developed rapidly into science, advances in photography made mass production of print easier, faster, and cheaper. The flat printing plate was replaced by cylindrical rollers, making easier to ink paper consistently, and presses could run even faster. Plates and presses began to be made with iron, increasing their speed and durability as well.

Today, printing is driven by the precision and power of computers, plates are made of plastic or metallic alloys, and the modern science of printing is more versatile and convenient yet.

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Color Models for Print and Screen

Color in print and on screen

Most industrial printing is done with four inks; Cyan, Magenta, Yellow, and Black. These are the primary colors for ink.
These four inks are referred to as the process colors, or just CMYK for short.
Unfortunately, nature can create many more colors than CMYK can create.

The range of colors that a color system can represent is called a gamut.
The images on your computer screen are created by Red, Green, and Blue light, the primary colors of light. Red Green and Blue Light can create far more colors than the 4 process inks. So, The RGB gamut is bigger than the CMYK gamut.


This is our first hurdle for good print files.

Be sure the files you submit are in CMYK color mode.



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The Printing Process

Most commercial presses have four rollers, one for each process color.
Each image plate is attached to one of these rollers to ink the paper with a grid of little color dots.
This enables the printer to precisely control the ink levels and how the different inks interact with each other.

The CYAN plate is rolled onto the paper like this,

and the MAGENTA is put down right after like this

and again with YELLOW,

and lastly, BLACK is put in to add depth and detail,

for a final printined image like this.
If you look closely at printed images, under a loupe or magnifiying glass, you should notice this grid of ink dots. To keep these dots of ink from landing right on top of each other, each grid of color is laid down at a different angle.

Commercial printing is usually produced at 133 or 150 lines of color dots per inch. This is referred to as a line screen. The angle at which the ink is laid down is called a screen angle.

To get a good quality image to print at 150 lpi (lines per inch), your images need to have 300 dpi (dots of color per inch). Your computer monitor only needs about 75 dots per inch to display a image and look good.

This measure of an image's detail is called resolution.

Your color bitmap images should have a resolution 300 dpi (dots per inch). This is enough detail to print images like photographs, patterned backgrounds, and paintings.

Text is created with mathematical curves, and solid lines. Since text is usually solid black, it doesn't need to be screened, ink is laid down as solid shapes instead of little dots of inks. This allows vector art to be output at the maximum resolution of the press. This is an incredible 2,780 dots per inch! You can't see that level of detail without a magnifying glass.

To get logos and flat areas of color as sharp as you would notice with the naked eye, these elements need to be created at 1,200 dpi.

This is our second hazard to good printing.

Make sure your bitmap images are at least 266 dot per inch
(for photographs and the like),
or 1,200 dpi (for 1-color bitmaps, logos, and such)


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Spot Color


Sometimes printers need to match a color exactly, for corporate logos or for a special print job, like metallic inks, or bright neon colours, or even an extra shiny varnish on top of the ink. To get consistent results, spot color inks are used.
Pantone® has created the most used and well known set of spot colors.
Cyan and Yellow inks can make different shades of green due to many factors, such as temperature, humidity, saturation of the ink, etc.


Pantone® makes a Green ink that will consistently be that Pantone® Green.

Due to the limits of the process, We cannot guarantee spot colors will register with CMYK colors. Basically, If Nomad prints CMYK, we have to run the printed piece back through the press and print spot colors on this second run. So, Spot colors are next to impossible to keep aligned with the first pass. To register spot color with CMYK, your costs will be greater due to the extra work involved.

Registration and Trapping

Trapping is the dark and scary art of making sure colors work together on the printed piece. The process of keeping the grids of ink colors aligned properly is called registration.
An example of Bad registration. Notice the fringe of color around the edges of the logo and text.

Resolution and Color Depth

One issue to watch-out for is a picture's resolution. Think of a digital picture as a grid of dots. On your computer screen, a picture only needs about 72 dots per inch (or dpi) to look good. If you look closely you will see these dots on screen and in print.
The picture below has a resolution of 72 dpi. On the left, it is displayed at 100%, on the right 400%. Notice when the image is magnified, the pixels (image dots) are enlarged, while the print dots will remain the same size, 300 per inch, and the detail suffers. This file has no extra detail to show when the magnification are increased.

More information on raster art (grids of dots of color) and vector (mathematical lines and curves) is available in the PhotoShop and Illustrator sections.

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Knockouts, Overprints, and Traps

When an object knocks-out its background, it removes all the ink underneath, and prints on blank paper. The opposite of this is overprinting, when the top object just prints right over any background ink. For small text (like black text on a colored background), overprinting is usually preferred. If you knock out small objects, they will often have a white halo.

Black and yellow inks, overprinting and knocking out.
Notice how the black that is set to knock-out will create a white fringe if it does not register perfectly.
Also, Note how Yellow ink mixes with the background when overprinting, changing the appearance drastically.

The dark side of Black

Black text on a white background is fairly common and will print as expected. When small black (as well as other colored) elements sit on top of a colored background, it will usually knock-out the background. Sometimes this is preferable, sometimes not so.
Printing large fields of black ink (or any one-color field) can be a problem. If the black area is just 100% black, black ink is applied to paper in one pass, and that's it. If dust in the air, or imperfections in the paper get in the way, the black area will have little white specks thoughout (called hickies), and this doesn't look professional.
An easy way to fix this is to make that field of black a rich black, or black created from a blend of all four process inks instead of just black ink. Rich black looks fuller and "blacker" than one color black, and hickies don't stand a chance againt it.

Nomad's formula for Rich Black is 50% Cyan, 40% Magenta, 30% Yellow, and 100% Black inks.

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Digital File formats and information

Pictures formats

Raster vs Vector

In 4-color printing, there are a few things to keep in mind with pictures. Pictures are usually in TIFF or EPS format. TIFF files keep an image's information as a grid of dots of color, or pixels. JpThis way of describing art (as a grid of pixels) is called Raster art. Raster graphics are usually manipulated in PhotoShop or a similar bitmap editor.

Text, and vector art (created in applications like Illustrator) is described differently than bitmap images. Vector art and text are understood by the computer as shapes based on mathematical calculations of lines and curve-control points on these lines.
Since Illustrator uses vector calculations instead of raster information, it can be resized easily without losing any detail.

PDF file format

PDF (Portable Document Format) files have great potential to eliminate many problems in printing electronic files from many different sources. PDF files include all the information needed to print that file (fonts, and how they behave, pictures, color information, etc.), and the format is supported across many computer platforms.
Unfortunately, PDF files don't live up to their billing quite yet (as of Spring 2003). PDF files can be tricky to create for print, and even then, font issues seem to happen often enough that Nomad cannot accept PDF files worry-free.

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